1. Field of the Invention
The present invention is directed to a system which determines whether to accept requests for wireless connection received from a networked device. The invention has particular utility in wireless ATM networks, in which it may be used by a base station to determine whether to accept or to deny requests for wireless connection received from one or more such devices.
2. Description of the Related Art
ATM (xe2x80x9casynchronous transfer modexe2x80x9d) is a protocol which was developed to address problems associated with transmitting multimedia data between networked devices. In particular, ATM networks are systems that negotiate and establish transmission parameters (e.g., bandwidth) prior to connecting two networked devices, xe2x80x9cpacketizexe2x80x9d different types of data (e.g., video and audio data) into cells based on the established transmission parameters, and then multiplex these cells so that they can be transmitted over a single communication line to a receiving device. The receiving device then checks the transmitted data for errors and, if any are present, requests retransmission of the data by the transmitting device.
Traditionally, ATM networks were wire-based, meaning that devices therein were interconnected using fiber optic cables or the like. Recently, however, wireless ATM networks have been developed which replace at least some of these fiber optic cables with point-to-point wireless connections, such as radio-frequency (xe2x80x9cRFxe2x80x9d) and infrared (xe2x80x9cIRxe2x80x9d) links. A wireless ATM network of this type is described in U.S. patent application Ser. No. 08/770,024, entitled xe2x80x9cMedium Access Control (MAC) Protocol For Wireless ATMxe2x80x9d (Assignee: Philips Electronics North America Corp.), the contents of which are hereby incorporated by reference into the subject application as if set forth herein in full.
In detail, the foregoing U.S. patent application describes a communications protocol (i.e., the MAC protocol) for a wireless ATM network, which increases quality of service, particularly in terms of allocated bandwidth, by first reserving and then scheduling resources required for data transmission. In that protocol, connection to a particular network device (e.g., a wireless terminal) is either accepted or denied based on whether that device has sufficient available buffer space to support the connection and based on whether there are sufficiently-available slots in a control data frame. While the MAC protocol has proven to be highly effective, there is room for improvement, particularly with respect to determining whether a connection should be accepted or denied.
Accordingly, there exists a need for a call admission control system which may be used with communications protocols, such as the MAC protocol, and which provides a relatively simple method of making connection determinations.
The present invention addresses the foregoing needs by providing a call admission control protocol, for use in a network base station or the like, which determines whether the base station should accept connection to a network device based on an amount of buffer space required to accommodate the connection and on a nominal cell rate at which cells are output from the buffer for the requested connection. By determining whether to accept connection based on these factors, the present invention increases the efficiency and the speed of communications protocols with which it is used.
According to one aspect, the present invention is a system (e.g., a method or computer-executable process steps) which operates in an ATM layer of a base station and which determines whether the base station should accept or deny a wireless connection to a network device. In operation, the base station receives a request to initiate the wireless connection to the network device, and the base station determines, in response to the request, a nominal cell rate at which cells are exiting from a buffer in the network device for the requested wireless connection. Thereafter, the base station determines an amount of buffer space in the network device required to accommodate the connection, and decides whether it should accept or deny the wireless connection based on the nominal cell rate and the amount of buffer space required to accommodate the connection.
In preferred embodiments of the invention, the request to initiate the wireless connection is made to the base station by a network device using a traffic descriptor for a real-time variable bit rate (xe2x80x9crt-VBRxe2x80x9d) connection. However, it is noted that the invention is not limited to use with rt-VBR traffic, and that the invention can be used with any one or more types of ATM traffic.
In other preferred embodiments of the invention, when the base station denies the wireless connection, it determines an amount of buffer space which is available in the buffer, and then varies the nominal cell rate based on the amount of available buffer space so as to accommodate the request. By virtue of this feature of the invention, it is possible to increase the range of requests that the base station can accommodate.
According to another aspect, the present invention is a call admission control system for use in an asynchronous transfer mode network having at least one base station which is connectable to at least one network device over a wireless link. The system receives a request from a network device and then determines whether the request is to initiate a connection between the base station and the network device or to release a connection between the base station and the network device. In a case that the request is to initiate a connection between the base station and the network device, the system (i) determines, in response to the request to initiate the wireless connection, a nominal cell rate at which cells are exiting from a buffer in the network device for the requested wireless connection, (ii) determines an amount of buffer space in the network device required to accommodate the connection, and (iii) decides whether to accept the connection based on the nominal cell rate and the amount of buffer space required to accommodate the connection. In a case that the request is to release a connection between the base station and the network device, the system releases one or more existing connections therebetween.
This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiment thereof in connection with the attached drawings.